Method for transmitting and receiving a signal to protect against erroneous feedback information

ABSTRACT

A method for providing precoding weights for data symbols of data control subframes includes generating a downlink frame having control subframes which individually correspond to one of a plurality of downlink data subframes, and inserting weight information into each of the control subframes, such that the weight information is to be applied to data symbols present in the corresponding one of the data subframes. The method further includes transmitting the control subframes and the inserted weight information to a receiving device.

CROSS-REFERENCE TO RELATED APPLICATIONS

Pursuant to 35 U.S.C. §119(a), this application claims the benefit ofearlier filing date and right of priority to Korean Application No.10-2006-0078416, filed on Aug. 18, 2006, the contents of which arehereby incorporated by reference herein in their entirety.

FIELD OF THE INVENTION

The present invention relates generally to wireless communicationsystems, and in particular, to a method for providing precoding weightsfor data symbols of data control subframes.

DISCUSSION OF THE RELATED ART

A transmit antenna array (TxAA) is a presently available scheme that isused to achieve transmit diversity. Examples of such schemes aredisclosed in standards materials developed according to the 3rdGeneration Partnership Project (3GPP). One TxAA scheme is applied to adedicated physical channel (DPCH) and a high speed downlink sharedchannel (HS-DSCH). A dual-stream TxAA technology is commonly considereda multiple-input multiple-output (MIMO) transmission technique for theHS-DSCH.

A typical dual-stream TxAA scheme is a closed loop technology which usestwo transmission antennas, multiplies the signal of a transmissionentity by a weight received from a reception entity, and transmits themultiplied resultant signal in an effort to improve system performance.

If the channel environment between a base station and associated userequipment (UE) is of sufficient quality, a dual-stream TxAA technologymay be used to add a single stream to a conventional TxAA transmissionto increase the data transfer rate. Such an arrangement multiples thesingle transmission stream by a new weight which is orthogonal to theconventional weight, and then transmits the multiplied result.

FIG. 1 is a block diagram depicting a typical TxAAtransmission/reception configuration implementing two antennas. Inparticular, this figure depicts a TxAA mode-1 system which detects areception (Rx) signal using a detection unit contained in the receivingentity, and extracts data from the Rx signal. A weight generation unitis shown calculating weights (w1 and w2) to maximize a signal-to-noiseratio (SNR) of the Rx signal. The calculated weights are subsequentlytransmitted to a transmitting entity.

The transmitting entity multiples the weights (w1 and w2) by thetransmission (Tx) signal, transmits the weight (w1) to a first antenna,and transmits the weight (w2) to a second antenna. If two Rx antennasare provided, Rx signals (r1 and r2) of the two individual antennas ofthe receiving entity may be represented by the following equations:

r ₁=(w ₁ h ₁₁ +w ₂ h ₁₂)s+n ₁

r ₂=(w ₁ h ₂₁ +w ₂ h ₂₂)s+n ₂

In these equations, s refers to a data symbol, h_(ij) refers to thechannel response transmitted from the j-th Tx antenna to the i-th Rxantenna, w_(i) refers to weight multiplied by the j-th antenna, andn_(i) and n₂ refer to additive white Gaussian noise (AWGN) contained ineach Rx signal.

Data symbol recovery of the TxAA mode-1 system may be accomplished usingthe following equation:

ŝ(w ₁ h ₁₁ +w ₂ h ₁₂)^(x) r ₁+(w ₁ h ₂₁ +w ₂ h ₂₂)*r ₂

An exemplary technique for calculating the weight includes using anEigen vector associated with a maximum Eigen value of a covariancematrix of a channel, as represented by the following equation:

Rw=λw

In this above equation, R relates to a covariance matrix of the channel.

A typical TxAA Mode-1 system utilizes a weight vector in the form of asingle bit, feeds back the weight vector, and allows only phaseinformation of a single bit to be fed back to each slot withoutincluding power information.

This Mode-1 system includes a pilot symbol of a downlink dedicatedphysical control channel (DPCCH), and transmits several orthogonal pilotsymbols to each of the two antennas. The UE then performs channelestimation of the two Tx antennas in slot units using a common pilotchannel (CPICH) of each antenna, calculates weights w₁ and w₂ of thetransmitting entity, and transmits phase and power control informationof each antenna to the base station.

A typically configured universal mobile telecommunications system (UMTS)terrestrial radio access network (UTRAN) analyzes reception (Rx)information according to the following table:

Slot # 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 FSM 0 0  π/2 0  π/2 0  π/2 0 π/2 0  π/2 0  π/2 0  π/2 0 1 π −π/2 π −π/2 π −π/2 π −π/2 π −π/2 π −π/2π −π/2 πThis technique for analyzing the Rx information employs one-bitinformation using a constellation rotation to diversify the Rx signal,such that at least four weights are used. For instance, weight (w₁) of afirst antenna is a fixed value denoted by the following:

$\omega_{1} = \frac{1}{\sqrt{2}}$

Weight (w₂) of a second antenna can be calculated, in conjunction withTable 1, using the following:

$w_{2} = {\frac{\sum\limits_{i = {n - 1}}^{n}{\cos \left( \Phi_{i} \right)}}{2} + {j \cdot \frac{\sum\limits_{i = {n - 1}}^{n}{\sin \left( \Phi_{i} \right)}}{2}}}$

Weight (w₂) of the second antenna can be calculated by the value(Φ_(i)), which corresponds to the feedback phase information of eachslot.

Note that a slight modification typically occurs at the edge of theframe. In order to adjust the phase of Slot 0, for example, theinformation of slot 13 of a previous frame is used instead of slot 14 ofthe previous frame. This is because the previous frame is used toacquire an average value on the basis of specific values (0, π) and(π/2, −π/2). A technique for calculating the average value includes theuse of the following equation.

$w_{2} = {\frac{{\cos \left( \Phi_{13}^{j - 1} \right)} + {\cos \left( \Phi_{0}^{j} \right)}}{2} + {j \cdot \frac{{\sin \left( \Phi_{13}^{j - 1} \right)} + {\sin \left( \Phi_{0}^{j} \right)}}{2}}}$

In the above equation,  ₀ ^(i) refers to a phase-adjusting command fedback to slot 0 of a current frame, and Φ₁₃ ^(j−1) refers to aphase-adjusting command fed back to slot 13 of a previous frame.

Since there is typically no feedback information before an initial step,the initial value may be set to:

$\omega_{1} = \frac{\left( {1 + j} \right)}{\sqrt{2}}$

Accordingly, after the lapse of the feedback operation, the followingequation may be used:

$w_{2} = {\frac{{\cos \left( {\pi/2} \right)} + {\cos \left( \Phi_{0} \right)}}{2} + {j \cdot \frac{{\sin \left( {\pi/2} \right)} + {\sin \left( \Phi_{0} \right)}}{2}}}$

As another example, a dual-stream TxAA scheme will now be described.Typically, a code reuse scheme for transmitting two streams for a singleorthogonal variable spreading factor (OVSF) code has been applied to theHS-DSCH of a WCDMA system, such that greater amounts of data can be sentover the HS-DSCH. For this purpose, a conventional TxAA scheme isextended to a dual-stream TxAA scheme. In general, the dual-stream TxAAscheme applies a conventional weight to a first stream, and appliesanother weight, orthogonal to the conventional weight, to a secondstream.

FIG. 2 is a block diagram depicting a typical dual-stream TxAAtransmitting entity implementing two antennas. In this figure, thetransmitting entity performs demultiplexing of information bits, suchthat the information bits are divided to form of a dual stream.Encoding, channel interleaving, and modulation are then applied to eachof the streams.

A corresponding weight is then multiplied by data transmitted via eachantenna, and the multiplied result is then transmitted. As an example,weights (v₁₁ and v₂₁) of the first stream are equal to those of theconventional TxAA scheme, and orthogonal weights (v₁₂ and v₂₂) of thesecond stream are applied to the second stream, such that it is notnecessary to change or add a routine which feed backs the weightselected by the UE to the base station (i.e., Node-B).

The TxAA system feeds back the selected weight to the Node-B, such thatthe Node-B creates and uses the weight on the basis of the receivedinformation. However, the Node-B is typically unable to recognizewhether a feedback information failure occurs. Therefore, if such afailure does occur, the TxAA system may use a distorted weight.

In such a scenario, the UE may decode data using an original weighthaving been fed back, but the TxAA system is unable to receivecorresponding data due to a difference between the weight of the Node-Band the weight of the UE. Therefore, the TxAA system will typicallydetermine the presence or absence of the feedback information failure,and also decode data using the same weight as the distorted weight usedby the Node-B, such that the system can receive desired data even thoughsystem performance may be slightly deteriorated.

Accordingly, the UE will typically require a specific method fordetermining whether the Node-B uses a normal weight or an erroneousweight. To accomplish this, an antenna verification procedure may beimplemented which utilizes a common pilot and a dedicated pilot. Thistechnique includes applying weight to the dedicated pilot, but not thecommon pilot. An example of such an antenna verification scheme isdisclosed in Appendix A of 3GPP TS 25.214 V4.4.0 (2002-3).

SUMMARY OF THE INVENTION

Features and advantages of the invention will be set forth in thedescription which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention. Theobjectives and other advantages of the invention will be realized andattained by the structure particularly pointed out in the writtendescription and claims hereof as well as the appended drawings.

In accordance with an embodiment, a method for providing precodingweights for data symbols of data control subframes includes generating adownlink frame having control subframes which individually correspond toone of a plurality of downlink data subframes, and inserting weightinformation into each of the control subframes, such that the weightinformation is to be applied to data symbols present in thecorresponding one of the plurality of data subframes. The method furtherincludes transmitting the control subframes and the inserted weightinformation to a receiving device.

In an aspect, each of the control subframes comprise a first portion anda second portion, and the method further includes inserting the weightinformation into the first portion of each of the control subframes.

In an aspect, each of the control subframes is defined by a single slot,and the second portion of each of the control subframes is defined by atleast two slots which follow the single slot.

In an aspect, each of the control subframes is arranged to border datasymbols present in the corresponding one of the plurality of datasubframes.

In an aspect, each of the control subframes comprise a plurality ofconsecutive slots, such that the weight information is inserted in afirst slot of the consecutive slots.

In an aspect, the method further includes inserting the weightinformation into only one of a plurality of slots which define each ofthe control subframes.

In an aspect, each of the data subframes comprise high speed physicaldata shared channel (HS-PDSCH) subframes and each of the controlsubframes comprise high speed shared control channel (HS-SCCH)subframes.

In an aspect, the receiving device is configured as user equipment.

In an aspect, the downlink frame is generated by a Node B operatingwithin a wireless communication system.

In an aspect, the method further includes transmitting the weightinformation in a slot which precedes a slot used to transmit data in thecorresponding data subframe.

In accordance with an alternative embodiment, a method for receivingprecoding weights applied to data symbols of data control subframesincludes receiving a plurality of data subframes, and receiving adownlink frame, which includes control subframes that individuallycorrespond to one of the plurality of data subframes. The method furtherincludes identifying weight information in each of the controlsubframes, and applying the weight information for each of the controlsubframes to corresponding data subframes of the plurality of datasubframes.

In accordance with another alternative embodiment, a transmitting entityoperable in a wireless communication system and configured to provideprecoding weights for data symbols of data control subframes includes aprocessor configured to generate a downlink frame having controlsubframes which individually correspond to one of a plurality ofdownlink data subframes, and insert weight information into each of thecontrol subframes, such that the weight information is to be applied todata symbols present in the corresponding one of the plurality of datasubframes. The transmitting entity further includes a transmitterconfigured to transmit the control subframes and the inserted weightinformation to a receiving device.

In accordance with yet another alternative embodiment, a portable devicefor receiving precoding weights applied to data symbols of data controlsubframes includes a receiver configured to receive a plurality of datasubframes, receive a downlink frame having control subframes whichindividually correspond to one of the plurality of data subframes. Theportable device further includes a processor configured to identifyweight information in each of the control subframes, and apply theweight information for each of the control subframes to correspondingdata subframes of the plurality of data subframes.

These and other embodiments will also become readily apparent to thoseskilled in the art from the following detailed description of theembodiments having reference to the attached figures, the invention notbeing limited to any particular embodiment disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of the presentinvention will become more apparent upon consideration of the followingdescription of preferred embodiments, taken in conjunction with theaccompanying drawing figures.

FIG. 1 is a block diagram depicting a typical TxAAtransmission/reception configuration implementing two antennas.

FIG. 2 is a block diagram depicting a typical dual-stream TxAAtransmitting entity implementing two antennas.

FIG. 3 depicts a method for transmitting feedforward information over adownlink dedicated channel according to an embodiment of the presentinvention.

FIG. 4 depicts a method for transmitting/receiving feedforwardinformation via the HS-SCCH according to an embodiment of the presentinvention.

FIG. 5 depicts a dedicated feedforward signaling message channel(DFSMCH) which may be assigned to a dedicated channel for transmittingthe D-FSM.

FIG. 6 depicts an overall timing relationship of the various schemes ofFIGS. 3-5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following detailed description, reference is made to theaccompanying drawing figures which form a part hereof, and which show byway of illustration specific embodiments of the invention. It is to beunderstood by those of ordinary skill in this technological field thatother embodiments may be utilized, and structural, electrical, as wellas procedural changes may be made without departing from the scope ofthe present invention. Wherever possible, the same reference numberswill be used throughout the drawings to refer to the same or similarparts.

First of all, various embodiments will be described in the context of adownlink frame structure formed in accordance with the requirements setout in the 3GPP WCDMA standards, but such embodiments are not limited tosuch standards and other techniques may be used for the frame structure.In addition, the terms “Node-B” and “UE” will be used to refer toparticular types of signal transmitters and signal receivers,respectively. However, a Node-B may be implemented using other deviceswhich can transmit downlink signals, and the UE may be implemented usingother devices which can receive such downlink signals.

In an embodiment, a method is provided for transmitting feedforwardinformation. In this embodiment, consider the scenario in which anunexpected failure occurs in weight information that is fed back fromthe UE to the Node-B. In this system, several transmission/reception(Tx/Rx) antennas transmit a data stream using a weight for each Txantenna. The Node-B informs the UE of the failure, such that the UE caneffectively decode data even though this failure has occurred in thefeedback weight information.

To accomplish this, the Node-B feeds back information to the UE (thisaction will also be referred to as feedforward). In this case, thefeedback information includes weight information to be multiplied bydata transmitted via each antenna.

To implement the above-noted operation, a downlink feedforward signalmessage (D-FSM) field may be assigned to a downlink dedicated channel(e.g., DL-DPCH or F-DPCH) and a high-speed downlink shared controlchannel (e.g., HS-SCCH). Also, the D-FSM field may be assigned to anadditional downlink dedicated channel (e.g., a downlink dedicatedfeedforward signal message channel (DL-DFSMCH)) and a downlink sharedcontrol channel (e.g., a downlink common feedforward signal messagechannel (DL-CFSMCH)). Various techniques for increasing signal Tx/Rxaccuracy by transmitting feedforward information over a variety ofchannels will now be described.

FIG. 3 depicts a method for transmitting feedforward information over adownlink dedicated channel according to an embodiment of the presentinvention. This figure depicts a downlink DPCH, and in particular, thenth DL DPCH, and an uplink DPCH, and in particular, the nth UL DPCH. Asan example, the uplink DPCH is spaced apart from the beginning point ofthe downlink DPCH by a predetermined distance corresponding to 1024chips. A primary common control physical channel (P-CCPCH) is used as areference for the timing relationship between channels. Note that theP-CCPCH may also be indicative of a timing point at which data of thecommon pilot channel (CPICH) is transmitted.

According to an embodiment, the UE generates an optimum weight using theabove-noted downlink CPICH. The UE also generates a feedback signalingmessage (FSM) bit according to the Mode-1 scheme, and transmits the FSMbit to the Node-B. The one-bit FSM bit is transmitted to the Node-B at aspecific time corresponding to about 70%-80% of each slot of the uplinkDPCH. Thereafter, the Node-B receives the FSM, and readjusts the weightof a beginning portion of each slot pilot field, instead of the edge ofthe downlink DPCH slot. Note that this pilot field occupies about60%-100%, or in some cases, 99%-100%, of each slot of the uplink DPCH.The just-noted portion of the slots is represented in FIG. 3 using by asmall-sized box of each slot of the DL DPCH.

When weight information is fed back to the Node-B over on the uplink, aweight can be applied to data which is to be transmitted from theNode-B. Therefore, because of the propagation delay between the downlinkand the uplink, a considerable time interval is typically arrangedbetween the end point of the FSM field of the uplink DPCH and the startpoint of the downlink pilot field.

The time interval is typically set to a specific time corresponding to aminimum of 1024 chips. Therefore, the start point of the downlink pilotfield corresponds to a specific point of about 60%-100% of the downlinkDPCH in consideration of the above-mentioned 1024 chips. Note that thetiming relationship between slot 5 of the uplink DPCH and slot 6 of thedownlink DPCH is disclosed for illustrative purposes only.

When the UE generates a weight and feeds back the weight, the Node-B mayapply the weight to predetermined points according to either of twomethods, which will be referred to herein as Option-1 and Option-2.According to Option-1, the FSM transmitted to the i-th slot of theuplink DPCH is applied to a corresponding time point of the downlink(i+1)-th slot. In other words, as shown in FIG. 3, the FSM information(E) applied to slot 4 of the uplink DPCH is applied to slot 5 of thedownlink DPCH. The Option-1 technique will typically consider only 1024chips because of the propagation delay from the uplink to the downlink.If the Option-1 technique generates the weight according to the Mode-1scheme described above, the Mode-1 scheme is characterized in such amanner that the weight is created by a combination between previousreception information D and current reception information E.

Option-2 typically assigns an additional spare time to theabove-mentioned minimum propagation delay, such that it applies the FSMtransmitted to the i-th slot to the time point of a downlink (i+2)-thslot. Option-1 is shown in an upper part of FIG. 3, and Option-2 isshown in a lower part of FIG. 3.

Another technique which will now be described allows the Node-B totransmit an actually-used weight to the UE regardless of the presence orabsence of an error or failure according to the above-mentioned timingrelationship. A first consideration includes various techniques forincluding a downlink feedforward signaling message (D-FSM information ina conventional downlink DPCH or fractional dedicated physical channel(F-DPCH)), and transmitting the resultant information.

As shown in “A1” and “A2” of FIG. 3, a first method includes the D-FSMfield in the downlink DPCH, and transmits the FSM bit received from theUE at intervals of a predetermined slot using the D-FSM field. As aresult, the bit mapping structure of the conventional DPCH is differentfrom that of the F-DPCH slot. However, since each of the two channels isused as a user dedicated channel, a newly-configured channel is onlyused by users utilizing two channels such that there is no influence inconventional users, thus resulting in a lack of backward compatibility.

In this case, the Node-B may recognize the weight after transmitting theFSM of the uplink DPCH according to the conventional timing diagramincluding a propagation delay, such that the D-FSM field location is setto a specific time at which feedback information transmission and 1024chips are considered. The specific time is typically at about 60%-100%of the downlink slot.

The weight received from the UE is applied to different time pointsusing, for example, Option-1 or Option-2, such that the FSM for acorresponding slot is transmitted according to individual options. Inother words, according to Option-1 as shown in FIG. 3, the feedforwardinformation contained in slots 4-7 of the DL DPCH are set to reception(Rx) feedforward information D, E, F, and G respectively received viaslots 3-6 of the UP DPCH.

According to Option-2, feedforward information contained in slots 4-7 ofthe DL DPCH are set to Rx feedforward information C, D, E, and Frespectively received via the slots 2-5 of the UP DPCH. Therefore, thefeedforward information of the Option-2 technique is spaced apart by theslots of the Option-1 technique by a predetermined distance of one slot.

If the UE receives the above-noted feedforward information, it decodesRx data using weights acquired via this information received from theNode-B, instead of using feedback information received in the UE itselfAccordingly, although the Node-B erroneously receives feedbackinformation of the UE so that an undesired weight is multiplied by thefeedback information, the UE can acquire weights actually multiplied byeach data, and decodes the data using the acquired weights, resulting inthe implementation of stable data reception.

FIG. 4 depicts a method for transmitting/receiving the above-describedfeedforward information via the HS-SCCH according to an embodiment ofthe present invention, and will now be described. In particular, atiming relationship between the HS-SCCH and the HS-PDSCH, which are usedas downlink shared channels, will also be described with reference toFIG. 4.

If the HS-PDSCH is established, the weight may be applied to theHS-PDSCH in the same or similar manner as in the downlink DPCH orF-DPCH.

If weight information is applied to the HS-PDSCH in slot units, theweight is typically readjusted to the edge of the HS-PDSCH slot. TheHS-PDSCH slot edge may be different from the start point of the pilotfield indicating the weight resetting point of the downlink DPCH, suchthat the resetting of the HS-PDSCH weight may be performed after thelapse of a predetermined time corresponding to M chips on the basis ofthe pilot start point of the downlink DPCH.

FIG. 4 also illustrates the coincidence of the weight resetting timepoint, and in particular, the exemplary case of M=0. This figure depictsthree slots of the HS-PDSCH as being formed from a single sub-frame, andMode-1 determining the weight of a current slot using a previous FSM anda current FSM. In the case of transmitting a single sub-frame, theHS-PDSCH requires not only the FSM bit applied to the three slots of thecorresponding sub-frame, but also another FSM bit information of thelast slot of a previous sub-frame received as an initial value.

FIG. 4 also shows three slots of the HS-SCCH as being formed from asingle sub-frame, which is similar to that of the HS-PDSCH. If each UEmonitors four HS-SCCH channels and at the same time recognizes that oneof the four HS-SCCH channels is assigned to the UE itself, the UErecognizes the HS-PDSCH on the basis of information of the correspondingchannel, and decodes data of the HS-PDSCH.

In this case, when the HS-SCCH recognizes a channel assigned to theHS-SCCH itself and data of the HS-PDSCH is decoded, an unexpected timedelay may occur. Due to the time delay, the HS-SCCH is transmittedearlier than the HS-PDSCH by two slots. The DPCH and the F-DPCH transmitindependent data fields in slot units, such that they may determine datato be transmitted prior to a transmission time of a corresponding field,regardless of the slot edge or frame edge.

In a manner which is different than the DPCH and F-DPCH, the HS-SCCH ischannel-coded by two parts, and is then transmitted in sub-frame unitssuch that it must determine all the information to be transmitted priorto the transmission time.

Referring still to FIG. 4, if a conventional weight application time isapplied to the HS-PDSCH sub-frame 2 (i.e., if the user desires to applyE, F, and G information according to Option-1 and desires to transmitthe D-FSM over the SH-SCCH), the feedforward information D of theprevious slot of the E information should be contained in the HS-SCCHsub-frame 2 such that D, E, F, and G information are transmitted to theHS-SCCH sub-frame 2. However, the D, E, F, and G information are notreceived in the Node-B in an uplink direction before a current timereaches the start point of the HS-SCCH sub-frame 2. Therefore, the D-FSMwhich includes the D, E, F, and G information cannot be transmitted overthe HS-SCCH. According to an embodiment, an additional time delay isadded to a propagation delay time required for receiving feedbackinformation via the uplink, such that the resultant data is transmittedas feedforward information.

The above-described additional time delay considers that the HS-SCCHperforms transmission of sub-frame units in a manner which differs fromthe dedicated channel (e.g., DPCH). Due to the additional time delay,the feedforward information can be transmitted over the conventionalHS-SCCH, resulting in the reduction of the number of unexpected errorscapable of being generated when the above-mentioned timing relationshipis disregarded.

In a manner similar to the HS-SCCH sub-frame 3, weight information C, D,E, and F received prior to the transmission time is transmitted via theD-FSM field of the HS-SCCH sub-frame 3, and weight information appliedto the HS-PDSCH sub-frame 3 are set to the values C, D, E, and F, suchthat an additional time delay can be assigned to the conventional weightapplication time.

If the weight applied to the HS-PDSCH is compared with the HS-PDSCH,which does not use conventional feedforward information, a time of twoslots is typically delayed as in Option-2, and a time of three slots istypically delayed as in Option-1, such that the feedforward informationcan be properly transmitted.

Terms “delay” and “time delay” will be considered in the context of thespecific case of M=0, for example, and where the conventional HS-PDSCHincludes only 1024 chips corresponding to a minimum propagation delay.However, if M=0, such that the DL DPCH and the HS-PDSCH have the sametiming point, an additional delay may be assigned to the timing point onthe basis of the DL DPCH. This additional delay can minimize a specifictime corresponding to the sum of two slots and one slot. The HS-SCCH istypically located prior to the HS-PDSCH by two slots.

The feedforward information D, capable of being applied to a third slotof the HS-PDSCH sub-frame 2, is inserted into sub-frame 3 indicatingthat the next sub-frame of the HS-SCCH is arranged at a location delayedby the two slots. According to Mode-1, feedforward information of aprevious slot is included such that it uses the additional delay of oneslot. Although this additional delay is indicative of a minimum delayrequired for transmitting the feedforward information via the HS-SCCH,the scope of the actual delay is not a requirement and may beestablished using different techniques.

If the propagation delay becomes longer because of channel conditions,for example, and information C, D, E, and F cannot be transmitted to theHS-SCCH sub-frame 3 (i.e., if only B, C, D, and E can be transmitted tothe HS-SCCH sub-frame 3), the weight applied to the HS-PDSCH may bedelayed by four slots according to Option-1, or delayed by three slotsaccording to Option-2. In such a scenario, provided that the weight iscreated by a previously-received FSM and a current FSM according toOption-1, the FSM corresponding to three slots contained in a singlesub-frame of the HS-PDSCH will include three information units, andinformation transmitted to the D-FSM will include the FSM information ofthe last slot of the previous sub-frame in order to implement theinitial value.

The embodiment of FIG. 4 includes the value D which corresponds to theweight of the last slot of the previous sub-frame although only E, F,and G data units are transmitted to the HS-PDSCH sub-frame 2, such thatD, E, F, and G data units are transmitted to the destination. Such anembodiment relates to a specific case for applying the weight in slotunits. However, situations in which collected feedback informationcapable of being received after transmitting the feedforward informationmay unavoidably assign a considerably long delay to the optimum weightsetting time point and its application time point. The channel capableof using MIMO may have low channel variation, such that the weightapplied to each slot slightly affects the performance improvement. Inthis case, the transmission of the D-FSM information of four bits mayencounter potentially significant overhead.

Another embodiment includes not applying feedforward information in slotunits, and instead applying such information in sub-frame units toprevent or minimize the above-noted delay and reduce overhead. Whenusing weight application to sub-frame units, the weight applied to thefirst of three slots may be equally applied to the remaining threeslots.

The Mode-2 technique uses information of a previous slot and FSM bitinformation of a current slot, such that there is a need to transmittwo-bit information. For instance, the weight can be applied to theHS-PDSCH sub-frame 3 using the last FSM bits (E and F) received prior tothe start point of the HS-SCCH sub-frame 3. In this case, the weightapplied to the HS-PDSCH generates a delay of 1 slot in Option-1, and maynot generate such a delay in Option-2.

The delay of this embodiment is shown under the condition of a minimumdelay. If a propagation delay becomes longer due to channel conditions,and E and F information cannot be transmitted to the HS-SCCH sub-frame 3(i.e., if only D and E information can be transmitted to the HS-SCCHsub-frame 3), the weight applied to the HS-PDSCH may generate a delay oftwo slots in Option-1, or may generate a delay of one slot in Option-2.

Yet another embodiment includes assigning a code channel capable oftransmitting the D-FSM, and using orthogonal variable spreading factor(OVSF) code resources, whenever downlink resources become exhausted.This example can maintain a conventional channel without any change.

FIG. 5 depicts a dedicated feedforward signaling message channel(DFSMCH) which may be assigned to a dedicated channel for transmittingthe D-FSM, as denoted by “C1.” This method is similar to theabove-described method for including D-FSM information in the downlinkDPCH channel or the F-DPCH channel, and then transmitting the resultantinformation.

According to the timing relationship associated with the downlink DPCH,the D-FSM field is assigned to some or all of 60%-100% of each slot. Inother words, compared with the embodiment of FIG. 3 showing that theD-FSM information is transmitted via the DL DPCH, the embodiment of FIG.5 substitutes the newly-defined DFSMCH for the DL DPCH in a manner thatis different than shown in FIG. 3. The other portions of FIG. 5 aresubstantially the same as that which is shown and described inconjunction with FIG. 3.

In yet another embodiment, an offset corresponding to (256×6) chips maybe assigned to the downlink DPCH, and the D-FSM field may be assigned tosome or all of a corresponding slot. Therefore, feedforward informationapplied to each slot can be equally applied to portions from the edge ofthe slot. The D-FSM information transmitted to each slot may be equal tothe FSM used for a corresponding downlink DPCH according to the Options1 and 2.

As indicated by item C2 of FIG. 5, a new shared channel for transmittingthe D-FSM information may be defined and transmitted as necessary. Thenewly-defined channel is denoted by a common feedforward signalingmessage channel (CFSMCH), and this method is similar to the method forloading the D-FSM information on the HS-SCCH and transmitting theresultant information.

According to this embodiment, data is transmitted according to thesub-frame structure, such that a current channel can be used as a sharedchannel. Provided that only one FSM information is independentlytransmitted to each slot via the conventional shared channel, thethree-slot and one-subframe structure is not satisfied due to theapplication problem of an initial value. Also, if all of the D-FSM arecoded to be appropriate for a single sub-frame, a delay may be assignedto the weight of the HS-PDSCH. To solve these situations, a techniquemay be used which independently transmits the FSM to each slotsimultaneously while maintaining the sub-frame structure.

The FSM of the last slot time of the previous sub-frame is transmittedto the first slot along with another FSM of the first slot time. Inother words, the first slot of sub-frame 1 includes feedforwardinformation corresponding to two slots, and only feedforward informationcorresponding to one slot is inserted into the remaining slots of thecorresponding sub-frame.

A method for applying the weight of the HS-PDSCH to the HS-PDSCH at thehighest speed will now be described. As shown by the arrows of FIG. 3,in order to apply D, E, F, and G values according to Option-1 inconsideration of only 1024 chips, the CFSMCH should be adjusted to belater than the HS-SCCH transmission timing point by a predeterminedperiod of two slots, such as that which is shown in FIG. 5. According toOption-2, C, D, E, and F values are used.

In this case, the D-FSM information transmitted to each slot transmitsthe FSM used for the downlink DPCH and a value prior to M chips (where0≦M≦2560, and FIG. 3 shows the case of M=0). In other words, if the userdesires to transmit data acquired when E, F, and G weights are appliedto the HS-PDSCH sub-frame 2, the sub-frame 3 of the “CFSMCH alt. 1” maytransmit D, E, F, and G feedforward information to three slots. TheHS-SCCH may be earlier than the HS-PDSCH by a specific time of twoslots, such that it can pre-notify the fact that data transmitted by theUE via the HS-PDSCH is transmitted to the HS-SCCH itself However, thereis no requirement that the CFSMCH inform which one of the UEs willreceive data via the HS-PDSCH such that data can be transmitted alongwith the sub-frame of the corresponding HS-PDSCH sub-frame.

In this embodiment, the number of bits of the first, second, and thirdslots, are different from each other. In order to acquire the samedecoding performance from all the bits, an amount of information may beincreased, such that the transmission (Tx) power of the first slot maybe increased by the increased amount of information.

If desired, the weight may be applied in frame units instead of usingslot units. A typical procedure includes assigning a delay to a weightapplication time by including D-FSM information in the HS-SCCH. However,one aspect of the present invention utilizes the same weight as that ofa conventional HS-PDSCH. In other words, the weight applied to the firstslot of the HS-PDSCH sub-frame may also be applied to the remaining twoslots. Therefore, there is no requirement for the DL CFSMCH to transmitthe FSM information to the second and third slots.

According the above-described embodiment, the DL SCFSMCH transmits 1-bitFSM information applied to the previous sub-frame, and 1-bit FSMinformation to be applied to a current sub-frame to slot 1, such that atotal of two bits are transmitted to slot 1.

In FIG. 5, Option-1 includes feedforward information (D and E) ofrecently-received two slots to the first slot in sub-frame 3 of the “DLCFSMCH alt. 1,” and Option-2 includes C and D information. According toOption-1, feedforward information D is applied to the last slot of theprevious sub-frame interval of sub-frame 3 and feedforward information Eis applied to the first slot of the current sub-frame. According toOption-2, the feedforward information C is applied to the last slot ofthe previous sub-frame interval of sub-frame 3 and feedforwardinformation D is applied to the first slot of the current sub-frame.

A method for establishing synchronization with the HS-SCCH and loadingthe D-FSM on the HS-SCCH according to an embodiment will now bedescribed. The D-FSM to be transmitted is channel-encoded in frameunits, and transmits a corresponding weight to the same point as that ofthe HS-SCCH. CFSMCH transmission is completed prior to the start pointof the HS-PDSCH, such that the weight information can also be applied atthe start point of the HS-PDSCH reception as may be necessary.

If desired, the weight may be applied in sub-frame units, as will now bedescribed. Mode-1 uses previous slot information and FSM bit informationof a current slot, such that it requires transmission of 2-bitinformation. If Mode-1 is applied to the HS-PDSCH sub-frame 3, thenweight is applied using E and F values indicating the last FSM bitsreceived prior to the start point of the HS-SCCH sub-frame 3. In thiscase, the weight applied to the HS-PDSCH generates a delay shorter thanthat of Option-1 by a predetermined time of one slot, and does notgenerate a delay according to Option-2.

If the propagation delay increases according to channel conditions, sothat E and F values are not transmitted to the HS-SCCH sub-frame 3(i.e., if only the D and E values can be transmitted to the HS-SCCHsub-frame 3), the weight applied to the HS-PDSCH is delayed by two slotsin Option-1, and delayed by one slot in Option-2.

FIG. 6 depicts an overall timing relationship of the various schemes ofFIGS. 3-5. If the feedforward information is transmitted over aconventional dedicated channel (e.g., DL-DPCH and DL-F-DPCH of FIGS. 3and 6), the channel will typically need to be resent in consideration ofthe relationship associated with a corresponding UE. If feedforwardinformation is transmitted using a shared channel such as the HS-SCCHshown in FIGS. 4 and 6, it may assign an additional delay to data. Tosolve the additional delay problem, the weight may be applied insub-frame units instead of using slot units.

FIGS. 5 and 6 depict DL DFSMCH alt. 1, DL DFSMCH alt.2, DCFSMCH alt. 1,and DL CFSMCH alt. 2 such that if a new channel for D-FSM information isestablished, an additional OVSF code may be assigned. If the UE receivesfeedforward information according to the above-described embodiments,the UE decodes Rx data using weights acquired from the Node-B viafeedforward information received over a variety of channels, instead ofits own feedback information. Although an undesired weight is multipliedby data because the Node-B receives erroneous feedback information fromthe UE, the UE can acquire information of weights actually multiplied byeach data, and decodes the data using the acquired weight information,resulting in the implementation of stable data reception.

The Node-B can transmit weight information used for actual datatransmission to the UE such that the UE can stably receive Tx data fromthe Node-B. A minimum delay is typically assigned to the transmission offeedforward information for transmitting weight information in the caseof using conventional dedicated and shared channels, such that thefeedforward information can also be accurately transmitted overconventional channels. The feedforward information can also betransmitted over newly-defined dedicated- and shared-channels, such thata time delay can be shorter than that of conventional channels.

In addition, the weight information may be transmitted in sub-frameunits such that it can reduce overhead required for transmittingfeedforward information under a low channel variation, and can minimizedelay required for transmitting the feedforward information.

Although the present invention may be implemented using the exemplaryseries of operations described herein, additional or fewer operationsmay be performed. Moreover, it is to be understood that the order ofoperations shown and described is merely exemplary and that no singleorder of operation is required.

The foregoing embodiments and advantages are merely exemplary and arenot to be construed as limiting the present invention. The presentteaching can be readily applied to other types of apparatuses andprocesses. The description of the present invention is intended to beillustrative, and not to limit the scope of the claims. Manyalternatives, modifications, and variations will be apparent to thoseskilled in the art.

What is claimed is:
 1. A method for transmitting signals at a basestation (BS) to a user equipment (UE) configured to operate in a multiinput multi output (MIMO) mode, the method comprising: receiving, by theBS from the UE, a weight parameter for use by the BS in a datatransmission; transmitting, by the BS to the UE, downlink controlinformation through a downlink control channel designated to the UE andcorresponding to a physical downlink shared channel, the downlinkcontrol channel designated to the UE being one of a plurality ofdownlink control channel candidates designated to the UE, wherein thetransmitted downlink control information includes precoding informationto be applied by the BS to downlink data, the precoding information tobe applied by the BS being based on the weight parameter received fromthe UE or not based on the weight parameter received from the UE;precoding, by the BS, the downlink data within a subframe based on theprecoding information; and transmitting, by the BS to the UE via theMIMO mode, the subframe including the precoded downlink data through thephysical downlink shared channel.
 2. The method of claim 1, wherein theprecoding includes precoding by subframe unit.
 3. The method of claim 1,wherein the precoding the downlink data within the subframe includesmultiplying the downlink data in the subframe by at least one weight. 4.The method of claim 1, wherein the precoding is based on change of aboundary of the subframe.
 5. The method according to claim 1, whereinthe precoding information is based on the weight parameter received fromthe UE.
 6. The method according to claim 1, wherein the precodinginformation is not based the weight parameter received from the UE. 7.The method according to claim 1, wherein the precoding informationcomprises precoding information for two slots of the subframe, andwherein the downlink control information including the precodinginformation is transmitted in a subframe immediately prior to thesubframe including the precoded downlink data.
 8. The method accordingto claim 1, wherein the downlink control channel is a newly definedchannel for transmitting the precoding information.
 9. The methodaccording to claim 1, wherein the MIMO mode scheme comprises a dualstream transmission mode, and wherein the downlink data is transmittedthrough a first stream and a second stream of the dual streamtransmission mode, with the first and the second streams beingtransmitted through respective ones of two antennas of the BS.
 10. Amethod for receiving signals from a base station (BS) by a userequipment (UE) configured to operate in a multi input multi output(MIMO) mode, the method comprising: transmitting, by the UE to the BS, aweight parameter for use by the BS in a data transmission; receiving, bythe UE from the BS, downlink control information through a downlinkcontrol channel designated to the UE and corresponding to a physicaldownlink shared channel, the downlink control channel designated to theUE being one of a plurality of downlink control channel candidatesdesignated to the UE, wherein the received downlink control informationincludes precoding information to be applied by the BS to downlink data,the precoding information to be applied by the BS being based on theweight parameter transmitted from the UE or not based on the weightparameter transmitted from the UE; and receiving, by the UE from the BSthrough the physical downlink shared channel, a subframe that includesthe downlink data, the downlink data having been precoded by the BSbased on the precoding information.
 11. The method of claim 10, whereinthe downlink data is precoded by the BS by subframe unit.
 12. The methodof claim 10, wherein the precoded downlink data in the subframe includesdownlink data that has been multiplied by at least one weight.
 13. Themethod of claim 10, wherein the downlink data is precoded based onchange of a boundary of the subframe.
 14. The method according to claim10, wherein the precoding information is based on the weight parameterreceived from the UE.
 15. The method according to claim 10, wherein theprecoding information is not based the weight parameter received fromthe UE.
 16. The method according to claim 10, wherein the precodinginformation comprises precoding information for two slots of thesubframe, and wherein the downlink control information including theprecoding information is received by the UE in a subframe immediatelyprior to receiving the subframe including the precoded downlink data.17. The method according to claim 10, wherein the downlink controlchannel is a newly defined channel for transmitting the precodinginformation.
 18. The method according to claim 10, wherein the MIMO modescheme comprises a dual stream transmission mode, and wherein thedownlink data is received through a first stream and a second stream ofthe dual stream transmission mode, with the first and the second streamsbeing received through respective ones of two antennas of the UE.
 19. Abase station (BS) configured to transmit signals to a user equipment(UE) configured to operate in a multi input multi output (MIMO) mode,the BS comprising: a receiver; a transmitter; and a processoroperatively connected to the receiver and the transmitter, the processorconfigured to: receive, from the UE, a weight parameter for use by theBS in a data transmission; transmitting, to the UE, downlink controlinformation through a downlink control channel designated to the UE andcorresponding to a physical downlink shared channel, the downlinkcontrol channel designated to the UE being one of a plurality ofdownlink control channel candidates designated to the UE, wherein thetransmitted downlink control information includes precoding informationto be applied by the BS to downlink data, the precoding information tobe applied by the BS being based on the weight parameter received fromthe UE or not based on the weight parameter received from the UE;precode the downlink data within a subframe based on the precodinginformation; and transmit, to the UE via the MIMO mode, the subframeincluding the precoded downlink data through the physical downlinkshared channel.
 20. A user equipment (UE) configured to receive signalsfrom a base station (BS) in a multi input multi output (MIMO) mode, theUE comprising: a receiver; a transmitter; and a processor operativelyconnected to the receiver and the transmitter, the processor configuredto transmit, to the BS, a weight parameter for use by the BS in a datatransmission; receive, from the BS, downlink control information througha downlink control channel designated to the UE and corresponding to aphysical downlink shared channel, the downlink control channeldesignated to the UE being one of a plurality of downlink controlchannel candidates designated to the UE, wherein the received downlinkcontrol information includes precoding information to be applied by theBS to downlink data, the precoding information to be applied by the BSbeing based on the weight parameter transmitted from the UE or not basedon the weight parameter transmitted from the UE; and receive, from theBS through the physical downlink shared channel, a subframe thatincludes the downlink data, the downlink data having been precoded bythe BS based on the precoding information.